When it becomes necessary to employ artificial feeding there are two principles upon which it may be conducted. The first and most extensively practised is to endeavour to obtain a food by modifying cow's milk, which corresponds as nearly as possible to the composition of average human milk. The second is to adapt the prepared milk to the needs of each particular infant, as suggested by the state of its digestive organs and existing nutrition and development. The first method seeks to bring the child up to the standard of the milk, the second to bring the milk to the standard of the child. This system of " prescription writing " as applied to milk, in cases of severe illness and great impairment of digestion, is more rational than the older method, but it presupposes much experience and care on the part of the physician.

Due regard must be had, of course, for the circumstances of those for whom an especially modified diet is ordered. For the very poor, milk is a serious item of expense, and cream and sugar may be out of the question. Condensed milk is usually cheaper in large cities than fresh cow's milk, for less care and expense is involved in its transportation, and it is accordingly much used by the poor. Moreover, in hot weather it keeps without ice, but for reasons given elsewhere (p. 95) it is never to be preferred when good fresh cow's milk is obtainable. It is deficient in protein, and this may be corrected by adding meat broth, beef juice, or egg albumin. It is also deficient in fat, and cod-liver oil may be added.

Cow's milk contains approximately half the quantity of sugar present in human milk.

Leeds says that the curd derivable from human milk is only one fifth as much as that of cow's milk, and there are other striking differences in regard to the quantity of casein precipitable by acid, as compared with the non-coagulable ingredients of both forms of milk.

For this reason cow's milk must be diluted for very young infants with two parts of water, in order to bring the casein nearer to the right proportion; but the addition of water reduces the percentage of fat and of sugar.

Escherich has shown that the infant fed upon diluted cow's milk has to take much more fluid than when nursed by breast milk to get the same quantity of nutriment, with consequent distention and possible enfeeblement of the stomach.

The disproportion of fat may be counterbalanced by using "top milk " - i. e., the upper layer which forms after the milk has stood for about eight hours, and which contains most of the cream. Milk sugar is then to be added in the proportion of one heaping teaspoon-ful to four ounces of the diluted milk. If cane sugar is used, which is less desirable, as it is more apt to ferment, only one teaspoonful to every six ounces is necessary.

From a quart of ordinary milk six ounces of top milk may be skimmed, seven ounces from rich, and five from poor milk. In lieu of top milk a mixture of equal parts of cream and of ordinary milk should be used (Holt).

When the milk causes dyspepsia, and large curds are vomited, it is well to substitute barley water for plain water in the same proportion.

If pearl barley is used it should be boiled a long time - for six or eight hours - the water being replaced as it evaporates. The proportion usually employed is two tablespoonfuls of barley to the quart of water. After careful straining through a linen cloth, a pinch of salt is added, and when cool the fluid is ready for use. Instead of pearl barley, one of the barley flours may be employed. This answers the purpose as well, and has the advantage of requiring much less time, boiling for half an hour being sufficient.

Holt gives the following formulae for an infant two months old . receiving twenty-four ounces a day:

Top milk............................... 8 ounces.

Barley water............................ 16 "

Milk sugar.............................. 6 heaping teaspoonfuls, or:

Cane sugar............................. 4 " "

The quantity is to be slightly increased, but the proportion may remain the same until the seventh or eighth month, when the mixture should be changed to -

Top milk...................................... 19 ounces.

Barley water................................... 19 "

Milk sugar..................................... 9 teaspoonfuls, or:

Cane sugar..................................... 5 "

In answer to the question, "Can a child one year old take plain cow's milk?" Holt says: "Many children can, but the majority do better when the milk is modified by the addition of cream and water, or by the use of diluted top milk. After standing six hours six ounces should be taken off from the top of the milk bottle and ten ounces more should then be poured off and the two mixed. This may be diluted with an equal quantity of water or barley water".

It is generally conceded that fresh raw cow's milk derived from a healthy cow, and carefully kept from germ contamination, is a more wholesome food for babies than milk which is either boiled, sterilised, Pasteurised, or peptonised. But in cities always, and everywhere in summer, it is difficult or impossible to obtain such milk, and one or other of the means of disinfection becomes imperative.

The heat required for sterilisation in some manner destroys the vital properties of nuclein of the milk (Starr). (See page 85).

Peptonised milk is used much less for infant feeding than formerly, for it has been found that they do not thrive if continuously fed upon it.